Guard implicit transaction usage on .net version >= 7.0

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/TransactionTest/DistributedTransactionTest.Windows.cs

@@ -51,7 +51,7 @@ namespace Microsoft.Data.SqlClient.ManualTesting.Tests
         [ConditionalFact(nameof(s_EnlistedTransactionPreservedWhilePooledCondition), Timeout = 10000)]
         public void Test_EnlistedTransactionPreservedWhilePooled()
         {
-#if NET
+#if NET7_0_OR_GREATER
             TransactionManager.ImplicitDistributedTransactions = true;
 #endif
             RunTestSet(EnlistedTransactionPreservedWhilePooled);